CARACAS, Venezuela (AP) -- Venezuela's government said it would seize a cement company owned by Mexico's Cemex SAB Monday night after failing to reach a deal on terms for its nationalization.

Vice President Ramon Carrizalez said that cement producers Lafarge SA of France and Switzerland's Holcim Ltd agreed to nationalization terms for their subsidiaries in Venezuela, and agreed to stay on as minority partners.

But as for Cemex, "it hasn't been possible to reach an agreement," Carrizalez said. "The period expires tonight, and the next step with this business is expropriation."

He noted that midnight would mark the end of a 60-day period for negotiating compensation laid out in a June decree by President Hugo Chavez.

There was no official reaction from Cemex, which says its Venezuela assets include three cement plants, 30 smaller concrete plants, a shipping terminal and other facilities.

But one Cemex official told The Associated Press that National Guard troops had already taken control of cement plants in Maracaibo and Barquisimeto on Monday evening, hours before the midnight deadline. The official spoke on condition of anonymity because she wasn't authorized to speak publicly about the subject.

Chavez called the nationalization of cement companies one of many "steps toward socialism," following nationalizations of telecommunications and electricity companies, the country's largest steel maker and major oil projects previously run by private oil companies.

"Tonight at midnight, we're going to take over the cement plants because the period is up today," Chavez said in a televised speech. "The cement factories pass over to state hands."

The vice president said Cemex asked for some $1.3 billion in compensation, calling that "well above its real value."

Company spokesman Jorge Perez, in Monterrey, Mexico, said earlier that Cemex had no immediate comment.

Oil Minister Rafael Ramirez said the government was prepared to take "operational control" of Cemex's facilities, similar to the transfer of authority during last year's nationalization of key oil projects.

"We're acting in accord with what's established in our laws," Ramirez said.

Of the three companies being nationalized, Cemex has the largest presence in Venezuela. It entered the country in 1994 when it bought out a Venezuelan cement company, and today has some 3,000 employees.

Venezuela agreed to pay $267 million to Lafarge and $552 million to Holcim in compensation within 60 days, Carrizalez said after the two signed accords agreeing to the terms.

Venezuela will obtain an 89-percent share of Lafarge's business in Venezuela and an 85-percent share of Holcim's unit in the country, while the two companies will stay on as minority partners, Carrizalez said.

Chavez, who did not attend the signing ceremony, pledged in a televised speech that state-run cement businesses will help bring down prices in Venezuela. He said Venezuelan cement has been "the most expensive in the world" because the companies "are in private hands and they set the price very high."

Venezuela's tax agency said earlier this month that Cemex owed US$37.3 million in unpaid taxes for 2006 and 2007. Ramirez said the company had "serious deficiencies" in both unpaid taxes and "environmental matters."

Before the deals were announced, Lafarge spokeswoman Claire Mathieu said in France that the company was "doing its best to protect the interests of its clients and staff" in Venezuela.

Lafarge has operated in Venezuela since 1994 through its subsidiary Fabrica Nacional de Cementos SACA, which runs two cement plants.

Holcim spokesman Peter Gysel said before the terms were announced that the company hoped to achieve "a solution that is satisfactory to both sides."

Associated Press writers Greg Keller in Paris, Frank Jordans in Geneva, and Mary Cuddehe in Mexico City contributed to this report.